Unprecedented chemical transformation of semicarbazones mediated by Wilkinson's catalyst

para-Nitrobenzaldehyde semicarbazone undergoes an unusual chemical transformation upon reaction with [Rh(PPh(3))(3)Cl] in the presence of trialkyl and dialkylamines (NR(2)R'; R = Et,(i)Pr, (n)Bu; R' = H or R' = R) via dissociation of the C-NH(2) bond and formation of a new C-NR(2) bond (where the NR(2) fragment is provided by the amine). The transformed semicarbazone ligand binds to rhodium as a dianionic C,N,O-donor to afford complexes of type [Rh(PPh(3))(2)(CNO-NR(2))Cl] (CNO-NR(2) = the coordinated semicarbazone ligand). Another group of semicarbazones (viz. salicylaldehyde semicarbazone, 2-hydroxyacetophenone semicarbazone, and 2-hydroxynaphthaldehyde semicarbazone) has also been observed to undergo a similar chemical transformation upon reaction with [Rh(PPh(3))(3)Cl] under similar experimental conditions as before, and these transformed semicarbazones bind to rhodium as dianionic O,N,O-donors affording complexes of the type [Rh(PPh(3))(2)(ONO(n)-NR(2))Cl] (ONO(n)-NR(2) = the coordinated semicarbazone ligand; n = 1-3). The structure of the [Rh(PPh(3))(2)(CNO-NEt(2))Cl] and [Rh(PPh(3))(2)(ONO(2)-NR(2))Cl] complexes has been determined. All the complexes show characteristic (1)H NMR signals. They also show intense absorptions in the visible and ultraviolet region. Cyclic voltammetry on the complexes shows an oxidative response within 0.52-0.97 V versus SCE and a reductive response within -1.00 to -1.27 V versus SCE, where both the responses are believed to be centered on the semicarbazone ligand.     

Synthesis, structure, and reactivity of ruthenium carboxylato and 2-oxocarboxylato complexes bearing the bis(3,5-dimethylpyrazol-1-yl)acetato ligand

A series of ruthenium(II) acetonitrile, pyridine (py), carbonyl, SO2, and nitrosyl complexes [Ru(bdmpza)(O2CR)(L)(PPh3)] (L = NCMe, py, CO, SO2) and [Ru(bdmpza)(O2CR)(L)(PPh3)]BF4 (L = NO) containing the bis(3,5-dimethylpyrazol-1-yl)acetato (bdmpza) ligand, a N,N,O heteroscorpionate ligand, have been prepared. Starting from ruthenium chlorido, carboxylato, or 2-oxocarboxylato complexes, a variety of acetonitrile complexes [Ru(bdmpza)Cl(NCMe)(PPh3)] (4) and [Ru(bdmpza)(O2CR)(NCMe)(PPh3)] (R = Me (5a), R = Ph (5b)), as well as the pyridine complexes [Ru(bdmpza)Cl(PPh3)(py)] (6) and [Ru(bdmpza)(O2CR)(PPh3)(py)] (R = Me (7a), R = Ph (7b), R = (CO)Me (8a), R = (CO)Et (8b), R = (CO)Ph) (8c)), have been synthesized. Treatment of various carboxylato complexes [Ru(bdmpza)(O2CR)(PPh3)2] (R = Me (2a), Ph (2b)) with CO afforded carbonyl complexes [Ru(bdmpza)(O2CR)(CO)(PPh3)] (9a, 9b). In the same way, the corresponding sulfur dioxide complexes [Ru(bdmpza)(O2CMe)(PPh3)(SO2)] (10a) and [Ru(bdmpza)(O2CPh)(PPh3)(SO2)] (10b) were formed in a reaction of the carboxylato complexes with gaseous SO2. None of the 2-oxocarboxylato complexes [Ru(bdmpza)(O2C(CO)R)(PPh3)2] (R = Me (3a), Et (3b), Ph (3c)) showed any reactivity toward CO or SO2, whereas the nitrosyl complex cations [Ru(bdmpza)(O2CMe)(NO)(PPh3)](+) (11) and [Ru(bdmpza)(O2C(CO)Ph)(NO)(PPh3)](+) (12) were formed in a reaction of the acetato 2a or the benzoylformato complex 3c with an excess of nitric oxide. Similar cationic carboxylato nitrosyl complexes [Ru(bdmpza)(O2CR)(NO)(PPh3)]BF4 (R = Me (13a), R = Ph (13b)) and 2-oxocarboxylato nitrosyl complexes [Ru(bdmpza)(O2C(CO)R)(NO)(PPh3)]BF4 (R = Me (14a), R = Et (14b), R = Ph (14c)) are also accessible via a reaction with NO[BF4]. X-ray crystal structures of the chlorido acetonitrile complex [Ru(bdmpza)Cl(NCMe)(PPh3)] (4), the pyridine complexes [Ru(bdmpza)(O2CMe)(PPh3)(py)] (7a) and [Ru(bdmpza)(O2CC(O)Et)(PPh3)(py)] (8b), the carbonyl complex [Ru(bdmpza)(O2CPh)(CO)(PPh3)] (9b), the sulfur dioxide complex [Ru(bdmpza)(O2CPh)(PPh3)(SO2)] (10b), as well as the nitrosyl complex [Ru(bdmpza)(O2C(CO)Me)(NO)(PPh3)]BF4 (14a), are reported. The molecular structure of the sulfur dioxide complex [Ru(bdmpza)(O2CPh)(PPh3)(SO2)] (10b) revealed a rather unusual intramolecular SO2-O2CPh Lewis acid-base adduct.     

Chemical control on the coordination mode of benzaldehyde semicarbazone ligands. synthesis, structure, and redox properties of ruthenium complexes

Reaction of benzaldehyde semicarbazone (HL-R, where H is a dissociable proton and R is a substituent (R = OMe, Me, H, Cl, NO(2)) at the para position of the phenyl ring) with [Ru(PPh(3))(3)Cl(2)] and [Ru(PPh(3))(2)(CO2)Cl2] has afforded complexes of different types. When HL-NO(2) and [Ru(PPh(3))(3)Cl2] react in solution at ambient temperature, trans-[Ru(PPh(3))(2)(L-NO2Cl] is obtained. Its structure determination by X-ray crystallography shows that L-NO2 is coordinated as a tridentate C,N,O-donor ligand. When reaction between HL-NO2 and [Ru(PPh(3))(3)Cl2] is carried out in refluxing ethanol, a more stable cis isomer of [Ru(PPh(3))(2)(L-NO2)Cl] is obtained. The trans isomer can be converted to the cis isomer simply by providing appropriate thermal energy. Slow reaction of HL-R with [Ru(PPh(3))(2)(CO2)Cl2] in solution at ambient temperature yields 5-[Ru(PPh(3))(2)(L-R)(CO)Cl] complexes. A structure determination of 5-[Ru(PPh(3))(2)(L-NO2)(CO)Cl] shows that the semicarbazone ligand is coordinated as a bidentate N,O-donor, forming a five-membered chelate ring. When reaction between HL-R and [Ru(PPh(3))(2)(CO2Cl2] is carried out in refluxing ethanol, the 4-[Ru(PPh(3))(2)(L-R)(CO)Cl] complexes are obtained. A structure determination of 4-[Ru(PPh(3))(2)(L-NO2)(CO)Cl] shows that a semicarbazone ligand is bound to ruthenium as a bidentate N,O-donor, forming a four-membered chelate ring. All the complexes are diamagnetic (low-spin d(6), S = 0). The trans- and cis-[Ru(PPh(3))(2)(L-NO2)Cl] complexes undergo chemical transformation in solution. The 5- and 4-[Ru(PPh(3))(2)(L-R)(CO)Cl] complexes show sharp NMR signals and intense MLCT transitions in the visible region. Cyclic voltammetry of the 5-[Ru(PPh(3))(2)(L-R)(CO)Cl] and 4-[Ru(PPh(3))(2)(L-R)(CO)Cl] complexes show the Ru(II)-Ru(III) oxidation to be within 0.66-1.07 V. This oxidation potential is found to linearly correlate with the Hammett constant of the substituent R.     

Ruthenium(II) polypyridyl complexes: potential precursors, metalloligands, and topo II inhibitors

Neutral and cationic mononuclear complexes containing both group 15 and polypyridyl ligands [Ru(kappa3-tptz)(PPh3)Cl2] [1; tptz=2,4,6-tris(2-pyridyl)-1,3,5-triazine], [Ru(kappa3-tptz)(kappa2-dppm)Cl]BF4 [2; dppm=bis(diphenylphosphino)methane], [Ru(kappa3-tptz)(PPh3)(pa)]Cl (3; pa=phenylalanine), [Ru(kappa3-tptz)(PPh3)(dtc)]Cl (4; dtc=diethyldithiocarbamate), [Ru(kappa3-tptz)(PPh3)(SCN)2] (5) and [Ru(kappa3-tptz)(PPh3)(N3)2] (6) have been synthesized. Complex 1 has been used as a metalloligand in the synthesis of homo- and heterodinuclear complexes [Cl2(PPh3)Ru(micro-tptz)Ru(eta6-C6H6)Cl]BF4 (7), [Cl2(PPh3)Ru(mu-tptz)Ru(eta6-C10H14)Cl]PF6 (8), and [Cl2(PPh3)Ru(micro-tptz)Rh(eta5-C5Me5)Cl]BF4 (9). Complexes 7-9 present examples of homo- and heterodinuclear complexes in which a typical organometallic moiety [(eta6-C6H6)RuCl]+, [(eta6-C10H14)RuCl]+, or [(eta5-C5Me5)RhCl]+ is bonded to a ruthenium(II) polypyridine moiety. The complexes have been fully characterized by elemental analyses, fast-atom-bombardment mass spectroscopy, NMR (1H and 31P), and electronic spectral studies. Molecular structures of 1-3, 8, and 9 have been determined by single-crystal X-ray diffraction analyses. Complex 1 functions as a good precursor in the synthesis of other ruthenium(II) complexes and as a metalloligand. All of the complexes under study exhibit inhibitory effects on the Topoisomerase II-DNA activity of filarial parasite Setaria cervi and beta-hematin/hemozoin formation in the presence of Plasmodium yoelii lysate.     

Experimental and computational investigation of C-N bond activation in ruthenium N-heterocyclic carbene complexes

A combination of experimental studies and density functional theory calculations is used to study C-N bond activation in a series of ruthenium N-alkyl-substituted heterocyclic carbene (NHC) complexes. These show that prior C-H activation of the NHC ligand renders the system susceptible to irreversible C-N activation. In the presence of a source of HCl, C-H activated Ru(I(i)Pr(2)Me(2))'(PPh(3))(2)(CO)H (1, I(i)Pr(2)Me(2) = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) reacts to give Ru(I(i)PrHMe(2))(PPh(3))(2)(CO)HCl (2, I(i)PrHMe(2) = 1-isopropyl-4,5-dimethylimidazol-2-ylidene) and propene. The mechanism involves (i) isomerization to a trans-phosphine isomer, 1c, in which hydride is trans to the metalated alkyl arm, (ii) C-N cleavage to give an intermediate propene complex with a C2-metalated imidazole ligand, and (iii) N-protonation and propene/Cl(-) substitution to give 2. The overall computed activation barrier (ΔE(++)(calcd)) corresponds to the isomerization/C-N cleavage process and has a value of +24.4 kcal/mol. C-N activation in 1c is promoted by the relief of electronic strain arising from the trans disposition of the high-trans-influence hydride and alkyl ligands. Experimental studies on analogues of 1 with different C4/C5 carbene backbone substituents (Ru(I(i)Pr(2)Ph(2))'(PPh(3))(2)(CO)H, Ru(I(i)Pr(2))'(PPh(3))(2)(CO)H) or different N-substituents (Ru(IEt(2)Me(2))'(PPh(3))(2)(CO)H) reveal that Ph substituents promote C-N activation. Calculations confirm that Ru(I(i)Pr(2)Ph(2))'(PPh(3))(2)(CO)H undergoes isomerization/C-N bond cleavage with a low barrier of only +21.4 kcal/mol. Larger N-alkyl groups also facilitate C-N bond activation (Ru(I(t)Bu(2)Me(2))'(PPh(3))(2)(CO)H, ΔE(++)(calcd) = +21.3 kcal/mol), and in this case the reaction is promoted by the formation of the more highly substituted 2-methylpropene.     

Coordination chemistry of 4-methyl-2,6,7-trioxa-1-phosphabicyclo[2,2,1]heptane: preparation and characterization of Ru(II) complexes

The complexes TpRu[P(OCH(2))(2)(OCCH(3)](PPh(3))Cl (2) [Tp = hydridotris(pyrazolyl)borate; P(OCH(2))(2)(OCCH(3)) (1) = (4-methyl-2,6,7-trioxa-1-phosphabicyclo[2,2,1]heptane] and TpRu(L)(PPh(3))Cl [L = P(OCH(2))(3)CEt (3), PMe(3) (4) or P(OMe)(3) (5)], (η(6)-C(6)H(6))Ru(L)Cl(2) [L = PPh(3) (6), P(OMe)(3) (7), PMe(3) (8), P(OCH(2))(3)CEt (9), CO (10) or P(OCH(2))(2)(OCCH(3)) (11)] and (η(6)-p-cymene)Ru(L)Cl(2) [L = P(OCH(2))(3)CEt (12), P(OCH(2))(2)(OCCH(3))P(OCH(2))(2)(OCCH(3)) (13), P(OMe)(3) (14) or PPh(3) (15)] have been synthesized, isolated, and characterized by NMR spectroscopy, cyclic voltammetry, mass spectrometry, and, for some complexes, single crystal X-ray diffraction. Data from cyclic voltammetry and solid-state structures have been used to compare the properties of (1) with other phosphorus-based ligands as well as carbon monoxide. Data from the solid-state structures of Ru(II) complexes show that P(OCH(2))(2)(OCCH(3)) has a cone angle of 104°. Cyclic voltammetry data reveal that the Ru(II) complexes bearing P(OCH(2))(2)(OCCH(3)) have more positive Ru(III/II) redox potentials than analogous complexes with the other phosphorus ligands; however, the Ru(III/II) potential for (η(6)-C(6)H(6))Ru[P(OCH(2))(2)(OCCH(3))]Cl(2) is more negative compared to the Ru(III/II) potential for the CO complex (η(6)-C(6)H(6))Ru(CO)Cl(2). For the Ru(II) complexes studied herein, these data are consistent with the overall donor ability of 1 being less than other common phosphines (e.g., PMe(3) or PPh(3)) or phosphites [e.g., P(OCH(2))(3)CEt or P(OMe)(3)] but greater than carbon monoxide.     

Formation of a dinuclear imido complex from the reaction of a ruthenium(VI) nitride with a ruthenium(II) hydride

The treatment of [Ru(L(OEt))(N)Cl(2)] (1; L(OEt)(-) = [Co(η(5)-C(5)H(5)){P(O)(OEt)(2)}(3)](-)) with Et(3)SiH affords [Ru(L(OEt))Cl(2)(NH(3))] (2), whereas that with [Ru(L(OEt))(H)(CO)(PPh(3))] (3) gives the dinuclear imido complex [(L(OEt))Cl(2)Ru(μ-NH)Ru(CO)(PPh(3))(L(OEt))] (4). The imido group in 4 binds to the two ruthenium atoms unsymmetrically with Ru-N distances of 1.818(6) and 1.952(6) ?. The reaction between 1 and 3 at 25 °C in a toluene solution is first order in both complexes with a second-order rate constant determined to be (7.2 ± 0.4) × 10(-5) M(-1) s(-1).     

Sigma-organyl complexes of ruthenium and osmium supported by a mixed-donor ligand

A series of vinyl, aryl, acetylide and silyl complexes [Ru(R)(kappa2-MI)(CO)(PPh3)2] (R = CH=CH2, CH=CHPh, CH=CHC6H4CH3-4, CH=CH(t)Bu, CH=2OH, C(C triple bond CPh)=CHPh, C6H5, C triple bond CPh, SiMe2OEt; MI = 1-methylimidazole-2-thiolate) were prepared from either [Ru(R)Cl(CO)(PPh3)2] or [Ru(R)Cl(CO)(BTD)(PPh3)2](BTD = 2,1,3-benzothiadiazole) by reaction with the nitrogen-sulfur mixed-donor ligand, 1-methyl-2-mercaptoimidazole (HMI), in the presence of base. In the same manner, [Os(CH=CHPh)(kappa2-MI)(CO)(PPh3)2] was prepared from [Os(CH=CHPh)(CO)Cl(BTD)(PPh3)2]. The in situ hydroruthenation of 1-ethynylcyclohexan-1-ol by [RuH(CO)Cl(BTD)(PPh3)2] and subsequent addition of the HMI ligand and excess sodium methoxide yielded the dehydrated 1,3-dienyl complex [Ru(CH=CHC6H9)(kappa2-MI)(CO)(PPh3)2]. Dehydration of the complex [Ru(CH=CHCPh2OH)(kappa2-MI)(CO)(PPh3)2] with HBF4 yielded the vinyl carbene [Ru(=CHCH=CPh2)(kappa2-MI)(CO)(PPh3)2]BF4. The hydride complexes [MH(kappa2-MI)(CO)(PPh3)2](M = Ru, Os) were obtained from the reaction of HMI and KOH with [RuHCl(CO)(PPh3)3] and [OsHCl(CO)(BTD)(PPh3)2], respectively. Reaction of [Ru(CH=CHC6H4CH3-4)(kappa2-MI)(CO)(PPh3)2] with excess HC triple bond CPh leads to isolation of the acetylide complex [Ru(C triple bond CPh)(kappa2-MI)(CO)(PPh3)2], which is also accessible by direct reaction of [Ru(C triple bond CPh)Cl(CO)(BTD)(PPh3)2] with 1-methyl-2-mercaptoimidazole and NaOMe. The thiocarbonyl complex [Ru(CPh = CHPh)Cl(CS)(PPh3)2] reacted with HMI and NaOMe without migration to yield [Ru(CPh= CHPh)(kappa2-MI)(CS)(PPh3)2], while treatment of [Ru(CH=CHPh)Cl(CO)2(PPh3)2] with HMI yielded the monodentate acyl product [Ru{eta(1)-C(=O)CH=CHPh}(kappa2-MI)(CO)(PPh3)2]. The single-crystal X-ray structures of five complexes bearing vinyl, aryl, acetylide and dienyl functionality are reported.     

Oxygen extrusion from amidate ligands to generate terminal Ta=O units under reducing conditions. How to successfully use amidate ligands in dinitrogen coordination chemistry

A series of mixed Cp* amidate tantalum complexes Cp*Ta(RNC(O)R')X(3) (where R = Me(2)C(6)H(3), (i)Pr, R' = (t)Bu, Ph, X = Cl, Me) have been prepared via salt metathesis and their fundamental reactivities under reducing conditions have been explored. Reaction of the tantalum chloro precursors with potassium graphite under N(2) or Ar leads to the stereoselective formation of the terminal tantalum oxo species, Cp*Ta=O(η(2)-RN=CR')Cl. This represents the formal extrusion of oxygen from the amidate ligand to the reduced tantalum center and is accompanied by the formation of the iminoacyl fragment bound to Ta(v). Amidate dinitrogen complexes, [Cp*TaCl(RNC(O)(t)Bu)](2)(μ-N(2)) (where R = Me(2)C(6)H(3), (i)Pr) were synthesized via salt metathesis from the known [Cp*TaCl(2)](2)(μ-N(2)) precursor, establishing that amidate ligands can support dinitrogen complexes, but not the reduction process often necessary for their synthesis.     

Synthesis,molecular structure,and C-C coupling reactions of carbeneruthenium(II) complexes with C5H5Ru(=CRR') and C5Me5Ru(=CRR') as molecular units

The ethene derivatives [(eta(5)-C(5)R(5))RuX(C(2)H(4))(PPh(3))] with R=H and Me, which have been prepared from the eta(3)-allylic compounds [(eta(5)-C(5)R(5))Ru(eta(3)-2-MeC(3)H(4))(PPh(3))] (1, 2) and acids HX under an ethene atmosphere, are excellent starting materials for the synthesis of a series of new halfsandwich-type ruthenium(II) complexes. The olefinic ligand is replaced not only by CO and pyridine, but also by internal and terminal alkynes to give (for X=Cl) alkyne, vinylidene, and allene compounds of the general composition [(eta(5)-C(5)R(5))RuCl(L)(PPh(3))] with L=C(2)(CO(2)Me)(2), Me(3)SiC(2)CO(2)Et, C=CHCO(2)R, and C(3)H(4). The allenylidene complex [(eta(5)-C(5)H(5))RuCl(=C=C=CPh(2))(PPh(3))] is directly accessible from 1 (R=H) in two steps with the propargylic alcohol HC triple bond CC(OH)Ph(2) as the precursor. The reactions of the ethene derivatives [(eta(5)-C(5)H(5))RuX(C(2)H(4))(PPh(3))] (X=Cl, CF(3)CO(2)) with diazo compounds RR'CN(2) yield the corresponding carbene complexes [(eta(5)-C(5)R(5))RuX(=CRR')(PPh(3))], while with ethyl diazoacetate (for X=Cl) the diethyl maleate compound [(eta(5)-C(5)H(5))RuCl[eta(2)-Z-C(2)H(2)(CO(2)Et)(2)](PPh(3))] is obtained. Halfsandwich-type ruthenium(II) complexes [(eta(5)-C(5)R(5))RuCl(=CHR')(PPh(3))] with secondary carbenes as ligands, as well as cationic species [(eta(5)-C(5)H(5))Ru(=CPh(2))(L)(PPh(3))]X with L=CO and CNtBu and X=AlCl(4) and PF(6), have also been prepared. The neutral compounds [(eta(5)-C(5)H(5))RuCl(=CRR')(PPh(3))] react with phenyllithium, methyllithium, and the vinyl Grignard reagent CH(2)=CHMgBr by displacement of the chloride and subsequent C-C coupling to generate halfsandwich-type ruthenium(II) complexes with eta(3)-benzyl, eta(3)-allyl, and substituted olefins as ligands. Protolytic cleavage of the metal-allylic bond in [(eta(5)-C(5)H(5))Ru(eta(3)-CH(2)CHCR(2))(PPh(3))] with acetic acid affords the corresponding olefins R(2)C=CHCH(3). The by-product of this process is the acetato derivative [(eta(5)-C(5)H(5))Ru(kappa(2)-O(2)CCH(3))(PPh(3))], which can be reconverted to the carbene complexes [(eta(5)-C(5)H(5))RuCl(=CR(2))(PPh(3))] in a one-pot reaction with R(2)CN(2) and Et(3)NHCl.     

Heterolytic cleavage of dihydrogen promoted by sulfido-bridged tungsten-ruthenium dinuclear complexes

A series of sulfido-bridged tungsten-ruthenium dinuclear complexes Cp*W(mu-S)(3)RuX(PPh(3))(2) (4a; X = Cl, 4b; X = H), Cp*W(O)(mu-S)(2)RuX(PPh(3))(2) (5a; X = Cl, 5b; X = H), and Cp*W(NPh)(mu-S)(2)RuX(PPh(3))(2) (6a; X = Cl, 6b; X = H) have been synthesized by the reactions of (PPh(4))[Cp*W(S)(3)] (1), (PPh(4))[Cp*W(O)(S)(2)] (2), and (PPh(4))[Cp*W(NPh)(S)(2)] (3), with RuClX(PPh(3))(3) (X = Cl, H). The heterolytic cleavage of H(2) was found to proceed at room temperature upon treating 5a and 6a with NaBAr(F)(4) (Ar(F) = 3, 5-C(6)H(3)(CF(3))(2)) under atmospheric pressure of H(2), which gave rise to [Cp*W(OH)(mu-S)(2)RuH(PPh(3))(2)](BAr(F)(4)) (7a) and [Cp*W(NHPh)(mu-S)(2)RuH(PPh(3))(2)](BAr(F)(4)) (8), respectively. When Cp*W(O)(mu-S)(2)Ru(PPh(3))(2)H (5b) was treated with a Br?nstead acid, [H(OEt(2))(2)](BAr(F)(4)) or HOTf, protonation occurred exclusively at the terminal oxide to give [Cp*W(OH)(mu-S)(2)RuH(PPh(3))(2)](X) (7a; X = BAr(F)(4), 7b; X = OTf), while the hydride remained intact. The analogous reaction of Cp+W(mu-S)(3)Ru(PPh(3))(2)H (4b) led to immediate evolution of H(2). Selective deprotonation of the hydroxyl group of 7a or 7b was induced by NEt(3) and 4b, generating Cp*W(O)(mu-S)(2)Ru(PPh(3))(2)H (5b). Evolution of H(2) was also observed for the reactions of 7a or 7b with CH(3)CN to give [Cp*W(O)(mu-S)(2)Ru(CH(3)CN)(PPh(3))(2)](X) (11a; X = BAr(F)(4), 11b; X = OTf). We examined the H/D exchange reactions of 4b, 5b, and 7a with D(2) and CH(3)OD, and found that facile H/D scrambling over the W-OH and Ru-H sites occurred for 7a. Based on these experimental results, the mechanism of the heterolytic H(2) activation and the reverse H(2) evolution reactions are discussed.     

Ruthenium mediated C-H activation of 2-(arylazo)phenols: characterization of an intermediate and the final organoruthenium complex

Reaction of 2-(arylazo)phenols with [Ru(PPh(3))(2)(CO)(2)Cl(2)] affords a family of organometallic complexes of ruthenium(II) of type [Ru(PPh(3))(2)(CO)(CNO-R)], where the 2-(arylazo)phenolate ligand (CNO-R; R = OCH(3), CH(3), H, Cl, and NO(2)) is coordinated to the metal center as tridentate C,N,O-donor. Another group of intermediate complexes of type [Ru(PPh(3))(2)(CO)(NO-R)(H)] has also been isolated, where the 2-(arylazo)phenolate ligand (NO-R) is coordinated to the metal center as bidentate N,O-donor. Structures of the [Ru(PPh(3))(2)(CO)(NO-OCH(3))(H)] and [Ru(PPh(3))(2)(CO)(CNO-OCH(3))] complexes have been determined by X-ray crystallography. All the complexes are diamagnetic and show characteristic (1)H NMR signals and intense MLCT transitions in the visible region. Both the [Ru(PPh(3))(2)(CO)(NO-R)(H)] and [Ru(PPh(3))(2)(CO)(CNO-R)] complexes show two oxidative responses on the positive side of SCE.     

Rhenium chemistry of diazabutadienes and derived iminoacetamides spanning the valence domain II-VI. Synthesis, characterization, and metal-promoted regiospecific imine oxidation

The reaction of diazabutadienes of type R'N=C(R)-C(R)=NR', L (R = H, Me; R' = cycloalkyl, aryl) with Re(V)OCl(3)(AsPh(3))(2) has furnished Re(V)OCl(3)(L), 1, from which Re(III)(OPPh(3))Cl(3)(L), 2, and Re(V)(NAr)Cl(3)(L), 3, have been synthesized. Chemical oxidation of 2(R = H) by aqueous H(2)O(2) and of 3(R = H) by dilute HNO(3) has yielded Re(IV)(OPPh(3))Cl(3)(L'), 5, and Re(VI)(NAr)Cl(3)(L'), 4, respectively, where L' is the monoionized iminoacetamide ligand R'N=C(H)-C(=O)-NR'(-). Finally, the reaction of Re(V)O(OEt)X(2)(PPh(3))(2) with L has furnished bivalent species of type Re(II)X(2)(L)(2), 6(X = Cl, Br). The X-ray structures of 1 (R = Me, R' = Ph), 3 (R = H, R' = Ph, Ar = Ph), and 4 (R = H, R' = cycloheptyl, Ar = C(6)H(4)Cl) are reported revealing meridional geometry for the ReCl(3) fragment and triple bonding in the ReO (in 1) and ReNAr (in 3 and 4 ) fragments. The cis geometry (two Re-X stretches) of ReX(2)(L)(2) is consistent with maximized Re(II)-L back-bonding. Both ReX(2)(L)(2) and Re(NAr)Cl(3)(L') are paramagnetic (S = (1)/(2)) and display sextet EPR spectra in solution. The g and A values of Re(NAr)Cl(3)(L') are, respectively, lower and higher than those of ReX(2)(L)(2). All the complexes are electroactive in acetonitrile solution. The Re(NAr)Cl(3)(L) species display the Re(VI)/Re(V) couple near 1.0 V versus SCE, and coulometric studies have revealed that, in the oxidative transformation of 3 to 4, the reactive intermediate is Re(VI)(NAr)Cl(3)(L)(+) which undergoes nucleophilic addition of water at an imine site followed by induced electron transfer finally affording 4. In the structure of 3 (R = H, R' = Ph, Ar = Ph), the Re-N bond lying trans to the chloride ligand is approximately 0.1 A shorter than that lying trans to NPh. It is thus logical that the imine function incorporating the former bond is more polarized and therefore subject to more facile nucleophilic attack by water. This is consistent with the regiospecificity of the imine oxidation as revealed by structure determination of 4 (R = H, R' = cycloheptyl, Ar = C(6)H(4)Cl).     

Dithiocarboxylate complexes of ruthenium(II) and osmium(II)

The ruthenium(II) complexes [Ru(R)(κ(2)-S(2)C·IPr)(CO)(PPh(3))(2)](+) (R = CH=CHBu(t), CH=CHC(6)H(4)Me-4, C(C≡CPh)=CHPh) are formed on reaction of IPr·CS(2) with [Ru(R)Cl(CO)(BTD)(PPh(3))(2)] (BTD = 2,1,3-benzothiadiazole) or [Ru(C(C≡CPh)=CHPh)Cl(CO)(PPh(3))(2)] in the presence of ammonium hexafluorophosphate. Similarly, the complexes [Ru(CH=CHC(6)H(4)Me-4)(κ(2)-S(2)C·ICy)(CO)(PPh(3))(2)](+) and [Ru(C(C≡CPh)=CHPh)(κ(2)-S(2)C·ICy)(CO)(PPh(3))(2)](+) are formed in the same manner when ICy·CS(2) is employed. The ligand IMes·CS(2) reacts with [Ru(R)Cl(CO)(BTD)(PPh(3))(2)] to form the compounds [Ru(R)(κ(2)-S(2)C·IMes)(CO)(PPh(3))(2)](+) (R = CH=CHBu(t), CH=CHC(6)H(4)Me-4, C(C≡CPh)=CHPh). Two osmium analogues, [Os(CH=CHC(6)H(4)Me-4)(κ(2)-S(2)C·IMes)(CO)(PPh(3))(2)](+) and [Os(C(C≡CPh)=CHPh)(κ(2)-S(2)C·IMes)(CO)(PPh(3))(2)](+) were also prepared. When the more bulky diisopropylphenyl derivative IDip·CS(2) is used, an unusual product, [Ru(κ(2)-SC(H)S(CH=CHC(6)H(4)Me-4)·IDip)Cl(CO)(PPh(3))(2)](+), with a migrated vinyl group, is obtained. Over extended reaction times, [Ru(CH=CHC(6)H(4)Me-4)Cl(BTD)(CO)(PPh(3))(2)] also reacts with IMes·CS(2) and NH(4)PF(6) to yield the analogous product [Ru{κ(2)-SC(H)S(CH=CHC(6)H(4)Me-4)·IMes}Cl(CO)(PPh(3))(2)](+)via the intermediate [Ru(CH=CHC(6)H(4)Me-4)(κ(2)-S(2)C·IMes)(CO)(PPh(3))(2)](+). Structural studies are reported for [Ru(CH=CHC(6)H(4)Me-4)(κ(2)-S(2)C·IPr)(CO)(PPh(3))(2)]PF(6) and [Ru(C(C≡CPh)=CHPh)(κ(2)-S(2)C·ICy)(CO)(PPh(3))(2)]PF(6).     

Trans --> cis isomerization of trans-[(dppm)2Ru(H)(L)][BF4] (L = P(OR)3) complexes: preparation of cis-[(dppm)2Ru(eta2-H2)(L)][BF4]2

A series of new dicationic dihydrogen complexes of ruthenium of the type cis-[(dppm)(2)Ru(eta(2)-H(2))(L)][BF(4)](2) (dppm = Ph(2)PCH(2)PPh(2); L = P(OMe)(3), P(OEt)(3), PF(O(i)Pr)(2)) have been prepared by protonating the precursor hydride complexes cis-[(dppm)(2)Ru(H)(L)][BF(4)] (L = P(OMe)(3), P(OEt)(3), P(O(i)Pr)(3)) using HBF(4).Et(2)O. The cis-[(dppm)(2)Ru(H)(L)][BF(4)] complexes were obtained from the trans hydrides via an isomerization reaction that is acid-accelerated. This isomerization reaction gives mixtures of cis and trans hydride complexes, the ratios of which depend on the cone angles of the phosphite ligands: the greater the cone angle, the greater is the amount of the cis isomer. The eta(2)-H(2) ligand in the dihydrogen complexes is labile, and the loss of H(2) was found to be reversible. The protonation reactions of the starting hydrides with trans PMe(3) or PMe(2)Ph yield mixtures of the cis and the trans hydride complexes; further addition of the acid, however, give trans-[(dppm)(2)Ru(BF(4))Cl]. The roles of the bite angles of the dppm ligand as well as the steric and the electronic properties of the monodentate phosphorus ligands in this series of complexes are discussed. X-ray crystal structures of trans-[(dppm)(2)Ru(H)(P(OMe)(3))][BF(4)], cis-[(dppm)(2)Ru(H)(P(OMe)(3))][BF(4)], and cis-[(dppm)(2)Ru(H)(P(O(i)Pr)(3))][BF(4)] complexes have been determined.     

Fully delocalized (ethynyl)(vinyl)phenylene bridged triruthenium complexes in up to five different oxidation states

Triruthenium [(dppe)(2)Ru{-C≡C-1,4-C(6)H(2)-2,5-R(2)-CH═CH-RuCl(CO)(P(i)Pr(3))(2)}(2)](n+) (4a, R = H; 4b, R = OMe) containing unsymmetrical (ethynyl)(vinyl)phenylene bridging ligands and displaying five well-separated redox states (n = 0-4) are compared to their bis(alkynyl)ruthenium precursors (dppe)(2)Ru{-C≡C-1,4-C(6)H(2)-2,5-R(2)-C≡CR'} (2a,b: R' = TMS; 3a,b: R' = H) and their symmetrically substituted bimetallic congeners, complexes {Cl(dppe)(2)Ru}(2){μ-C≡C-1,4-C(6)H(2)-2,5-R(2)-C≡C} (A(a), R = H; A(b), R = OMe) and {RuCl(CO)(P(i)Pr(3))(2)}(2){μ-CH═CH-1,4-C(6)H(2)-2,5-R(2)-CH═CH} (V(a), R = H; V(b), R = OMe) as well as the mixed (ethynyl)(vinyl)phenylene bridged [Cl(dppe)(2)Ru-C≡C-1,4-C(6)H(4)-CH═CH-RuCl(CO)(P(i)Pr(3))(2)] (M(a)). Successive one-electron transfer steps were studied by means of cyclic voltammetry, EPR and UV-vis-NIR-IR spectroelectrochemistry. These studies show that the first oxidation mainly involves the central bis(alkynyl) ruthenium moiety with only limited effects on the appended vinyl ruthenium moieties. The second to fourth oxidations (n = 2, 3, 4) involve the entire carbon-rich conjugated path of the molecule with an increased charge uniformly distributed between the two arms of the molecules, including the terminal vinyl ruthenium sites. In order to assess the charge distribution, we judiciously use (13)CO labeled analogues to distinguish stretching vibrations due to the acetylide triple bonds and the intense and charge-sensitive Ru(CO) IR probe in different oxidation states. The comparison between complex pairs 4a,b(n+) (n = 0-3), A(a,b)(n+) and V(a,b)(n+) (n = 0-2) serves to elucidate the effect of the methoxy donor substituents on the redox and spectroscopic properties of these systems in their various oxidation states and on the metal/ligand contributions to their frontier orbitals.     

Amino-closo-dodecaborate--a new ligand in coordination chemistry

The synthesis and characterization of three ruthenium complexes [Bu(3)MeN][Ru(PPh(3))(2)(NH(2)-B(12)H(11))Cl], [Bu(4)N][Ru(dppb)(NH(2)-B(12)H(11))Cl] and [RuCO(PPh(3))(2)(NH(2)-B(12)H(11))] with amino-closo-dodecaborate as the coordinating ligand are described.     

New highly stable metallabenzenes via nucleophilic aromatic substitution reaction

Treatment of the ruthenabenzene [Ru{CHC(PPh(3))CHC(PPh(3))CH}Cl(2)(PPh(3))(2)]Cl (1) with excess 8-hydroxyquinoline in the presence of CH(3)COONa under air atmosphere produced the S(N)Ar product [(C(9) H(6)NO)Ru{CHC(PPh(3))CHC(PPh(3))C}(C(9)H(6)NO)(PPh(3))]Cl(2) (3). Ruthenabenzene 3 could be stable in the solution of weak alkali or weak acid. However, reaction of 3 with NaOH afforded a 7:1 mixture of ruthenabenzenes [(C(9)H(6)NO)Ru{CHC(PPh(3))CHCHC}(C(9)H(6)NO)(PPh(3))]Cl (4) and [(C(9)H(6)NO)Ru{CHCHCHC(PPh(3))C}(C(9)H(6)NO)(PPh(3))]Cl (5), presumably involving a P-C bond cleavage of the metallacycle. Complex 3 was also reactive to HCl, which results in a transformation of 3 to ruthenabenzene [Ru{CHC(PPh(3))CHC(PPh(3))C}Cl(2)(C(9)H(6)NO)(PPh(3))]Cl (6) in high yield. Thermal stability tests showed that ruthenabenzenes 4, 5, and 6 have remarkable thermal stability both in solid state and in solution under air atmosphere. Ruthenabenzenes 4 and 5 were found to be fluorescent in common solvents and have spectral behaviors comparable to those organic multicyclic compounds containing large π-extended systems.     

The chemistry of cadmium-thiocarboxylate derivatives: synthesis, structural features, and application as single source precursors for ternary sulfides

Novel heterobimetallic complexes [(PPh(3))(2)Cu(μ-SCOPh)(2)Cd(SCOPh)] (2a), [(PPh(3))(2)Cu(μ-SCOth)(2)Cd(SCOth)] (2b), [(PPh(3))(2)Ag(μ-SCOth)(2)Cd(SCOth)] (3a), [(PPh(3))(2)Ag(μ-SCOth)(2)Cd(H(2)O)(SCOth)] (3b), [(PPh(3))(2)Ag(μ-SCOPh)(2)Cd(SCOPh)] (3c), and a bimetallic complex [PPh(3)Cd(μ-SCOth)SCOth](2)·CH(2)Cl(2) (5) (th = thiophene) were prepared and characterized by single crystal X-ray diffraction analysis. A coordination polymer [Cd(SCOPh)(2)](n) (4) has also been characterized structurally that exhibited metal-like electrical conductivity. The heterobimetallic complexes on pyrolyzing under controlled conditions yielded ternary sulfides of composition CuCd(7)S(8), CuCd(10)S(11), Ag(2)Cd(8)S(9), and Ag(2)Cd(5)S(6), which have been characterized by SEM-EDX and X-ray diffractometry. Photophysical properties and electrical conductivities of the sulfides have also been studied.     

Unprecedented luminescent heteropolynuclear aggregates with gold thiolates as building blocks

The reaction of [AuCl(P-N)], in which P-N represents a heterofunctional phosphine ligand, with pentafluorothiophenol, HSC(6)F(5), gives the thiolate gold derivatives [Au(SC(6)F(5))(P-N)] (P-N = PPh(2)py (1), PPh(2)CH(2)CH(2)py (2), or PPhpy(2) (3)). Complex [Au(SC(6)F(5))(PPh(2)py)] (1) reacts with [Au(OTf)(PPh(2)py)] in a 1:1 or 1:2 molar ratio to afford the di- or trinuclear species [Au(2)(μ-SC(6)F(5))(PPh(2)py)(2)]OTf (4) and [Au(3)(μ(3)-SC(6)F(5))(PPh(2)py)(3)](OTf)(2) (5), with the thiolate acting as a doubly or triply bridging ligand. The reactivity of the mononuclear compounds [Au(SC(6)F(5))(P-N)] toward silver or copper salts in different ratios has been investigated. Thus, the treatment of [Au(SC(6)F(5))(P-N)] with Ag(OTf) or [Cu(NCMe)(4)]PF(6) in a 1:1 molar ratio gives complexes of stoichiometry [AuAg(OTf)(μ-SC(6)F(5))(P-N)] (P-N = PPh(2)py (6), PPh(2)CH(2)CH(2)py (7), or PPhpy(2) (8)) or [AuCu(μ-SC(6)F(5))(P-N)(NCMe)]PF(6) (P-N = PPh(2)py (9), PPh(2)CH(2)CH(2)py (10), or PPhpy(2) (11)). These complexes crystallize as dimers and display different coordination modes of the silver or copper center, depending on the present functionalized phosphine ligand. The treatment of [Au(SC(6)F(5))(PPh(2)py)] with silver and copper compounds in other molar ratios has been carried out. In a 2:1 ratio, the complexes [Au(2)M(μ-SC(6)F(5))(2)(μ-PPh(2)py)(2)]X (M = Ag, X = OTf (12); M = Cu, X = PF(6) (13)) are obtained. The same reaction in a 4:3 molar ratio affords the species [Au(4)M(2)(μ-SC(6)F(5))(3)(μ-PPh(2)py)(4)]X(3) (M = Ag, X = OTf (14); M = Cu, X = PF(6) (15)). The crystal structures of some of these complexes reveal different interactions among the metallic d(10) centers. The complexes display dual emission. The band at higher energy has been attributed to intraligand (IL) transitions, and the one at lower energy has been assigned to a ligand to metal (LM) charge transfer process. The latter emission is modulated by the heterometal (silver or copper).